We’ll walk you through the steps using a sharp and clean Eagle design. This one’s vector-perfect, imported from Illustrator, so we’re working with an ideal setup for learning. Let’s roll!
WHAT IS CHOKING OR TRAPPING?
In screen printing, choking means slightly reducing the size of your white base underlayer so it doesn’t peek out around the edges of your top colors. Conversely, trapping involves overlapping colors slightly to avoid registration gaps. Think of it as the "glue" that holds your design together when printed.
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BEFORE WE START: IMPORTANT NOTES
- RESOLUTION MATTERS: Work at 300 DPI minimum. For finer details or text-heavy designs, consider 600 DPI to maintain control over pixels.
- DON’T RESIZE AFTER SEPARATIONS: Once you’ve begun, resizing your artwork can distort your separations.
- SPOT COLORS ARE YOUR FRIEND: Always separate your design using spot colors for compatibility across Adobe products and RIP software.
STEP-BY-STEP PROCESS
SET UP YOUR FILE
Open your design in Photoshop. For this tutorial, we’re working with a vector-based design imported as a smart object from Illustrator. Ensure your resolution is 300 DPI or higher. Create channels for each color using the Magic Wand Tool and save selections for all major colors (e.g., gold, red, grays).
BUILD YOUR WHITE BASE
A white base acts as the foundation for your design, ensuring vibrant colors even on dark garments.
- Create a new channel by going to the Channels panel and clicking “New Channel.” Name it "White Base" and set the color to white with 100% opacity.
- Hold down Command (Mac) or Ctrl (Windows) and select all color channels that need a white base. Go to Edit > Fill and fill the selection with black in the "White Base" channel.
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CHOKE YOUR WHITE BASE
- Select the White Base channel by holding Command/Ctrl and clicking it.
- Contract the selection by going to Select > Modify > Contract and entering 1 pixel (at 300 DPI, this equals a 0.5-point choke). Adjust as needed—at 600 DPI, you can go down to finer increments like 1.5 pixels.
- Invert the selection with Select > Inverse and press Delete to remove the outermost pixels.
ADDRESS HIGHLIGHT WHITE
Highlight whites can overlap your top colors if left unchecked. To ensure accuracy:
- Select your “Highlight White” channel.
- Use the Apply Image command (Image > Apply Image) and set the source as “Highlight White,” using the “Multiply” blend mode.
- Adjust opacity or tone as needed. This step ensures your highlight white aligns perfectly without unnecessary overlaps.
FINE-TUNE OTHER CHANNELS
For a smooth print, repeat the choke process on your Spot Black or any other colors that overlap. Use a similar pixel contraction to pull back colors slightly and prevent "fuzzy edges."
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PRO TIPS FOR CLEAN SEPARATIONS
- CHOOSE THE RIGHT DPI: Higher resolutions (600 DPI) allow for finer control, especially with halftones or intricate text.
- PREVIEW YOUR DESIGN: Turn on all channels and zoom in to ensure everything aligns.
- WORK NON-DESTRUCTIVELY: Save frequently and use layer copies if you need to make adjustments.
FINAL CHECK
Turn on all layers and channels to preview the final design. Look for smooth overlaps, crisp edges, and no unintended white peeking through. Adjust as needed, and you’re ready to print!
WHY THIS MATTERS
Mastering chokes and traps ensure your prints look professional, avoids registration mishaps, and maintains the integrity of your design, even under the pressures of wet-on-wet printing or high-speed production.
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